1. Field of the invention
The present invention concerns a current amplifier power circuit and the application of this circuit in a selective triggering device (solid-state relay), specifically adapted to control the triggering of an alarm.
2. Description of the prior art
There are already known transistor amplifier power circuits which comprise a plurality of bipolar transistors connected by their collectors and their emitters between a maximum potential line and a minimum potential line and connected in cascade, but these circuits entail the use of a considerable number of transistors when there is a requirement to withstand a potential difference significantly greater than the maximum potential difference tolerable by each of the transistors between its collector and its emitter, substantially double this maximum tolerable difference, for example.
One object of the invention is a current amplifier power circuit which can withstand, with a limited number of components, an overall voltage significantly higher than the maximum voltage tolerable by the components in isolation.
Another object of the invention is a selective triggering device or solid-state relay equipped with a power circuit of the aforementioned type which is adapted to supply power only in the presence of an input signal and so procures failsafe control of the load circuit to be triggered. The latter is sometimes itself of the failsafe type; in the case of an alarm circuit, an alarm device is triggered when said alarm circuit ceases to be energized through the power circuit.
The invention is also directed to a triggering device of the aforementioned type adapted to be controlled by logic signals.
The invention also applies to a device of the aforementioned type adapted to provide galvanic isolation between the input logic signals and the power circuit.
The invention is also directed to be a switchable triggering device adapted to react to input logic signals according to various predetermined operating modes.